The game is heavily based on Gnostic ideas, but if you're into the Xeno series of games already, that's not new. What is new is how it takes those ideas, but almost completely separates it from Christianity. In Xenosaga, the Christian inspiration is clear as day, and the same would be true of later entries like XC2, if not for the translation job removing most of it. But XC1 has the Gnostic ideas and themes, without any of the real world religion being core to the plot.
The most important part of that is the Monado. Quick rundown for people who don't know about Gnostic stuff, the Monad is a way to refer to the "true" Creator, who is typically depicted as the spiritual light of Creation. The closer someone's soul is to the Monad, the more enlightened they are. The physical world was made by the Demiurge, a being that was born far from the Monad, and didn't know about the Light, so he created the world and seeded it with life, whose souls are fragments of the Light. The Demiurge isn't good for doing this, since Gnostic faith usually portrays the spirit as good, and physical reality as bad. Instead, the Demiurge is considered misguided, creating the world in search of companionship by selfishly trapping souls away from the true Light. The goal of life is to find Gnosis, or divine knowledge, and reconnect your soul to the Monad's light.
This stuff is almost exactly how Xenoblade's plot is structured. Zanza used the Monado's light to create Bionis, desperate for friendship, but arrogantly believing his creations were bound to him like slaves. Shulk's power is made stronger by unlocking more of the Monado's light, and eventually, he rejects Zanza to find his own Monado, which is both the actual sword, and the Light of Creation in it's true, spiritual form. The only difference in ideas is that Xenoblade, like Monolithsoft's other games, sees the physical world as having value, and so Shulk rejects the idea of being controlled by a god, or becoming a god to rule over others. Instead, he creates a world without gods, so that people can live in peace with each other, not as slaves to a divine will.
I think it's really good stuff. I'm biased in that I look into history, theological history being one of the areas of interest, so this application of Gnostic philosophy being more than window dressing gets me excited. But I hope that people who didn't know about that connection can appreciate Xenoblade's plot more because of that.